Compilare: user.cpp: In function ‘bool comp(std::pair<int, int>, std::pair<int, int>)’: user.cpp:18:30: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] return (l.f<r.f || l.f==r.f && l.s<r.s); ^ user.cpp: In function ‘int main()’: user.cpp:31:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (unsigned int i=1; i<n; i++) { ^ user.cpp:39:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p!=i) { ^